The relation of psychosocial forms of occupational stress to mental and physical health is examined in a cross-sectional study of 1930 blue collar workers in a tire, rubber, plastics and chemical factory. The data include (1) expert judges' ratings of potentially stressful objective (psychosocial) conditions of work (e.g., workload, interpersonal pressures, responsibility); (2) questionnaire indicators of perceived stress (e.g., subjective reports of workload, role conflict, or responsibility pressures; (3) a wide range of indicators of physical and mental health from both questionnaires and physical examinations; and (4) measures of a variety of "conditioning" variables which are expected to "specify" or "moderate" the relation of objective work conditions and/or perceived stress to health. Self-reported and environmentally assessed exposure to physical-chemical hazards (i.e., dust, fumes, chemicals, heat and noise) constitutes one set of conditioning variables. The relation of psychosocial job stress to health will be examined net of, and in conjunction with, physical-chemical exposure. The data on actual psychosocial and physical-chemical working conditions are unique, allowing empirical analysis of many important theoretical and applied questions not adequately answered in prior research.